Permalinks

Permalinks are the permanent URLs of your blog posts or pages on your WordPress site.

Go to Settings > Permalinks.
Select one of the available formats:
Plain: http://www.yourwebsite.com/?p=123
Day and name: http://www.yourwebsite.com/2008/03/31/sample-post/
Month and name: http://www.yourwebsite.com/2008/03/sample-post/
Numeric: http://www.yourwebsite.com/archives/123
Post name: http://www.yourwebsite.com/sample-post
Custom structure in the box enter the custom structure you want to use. For example: /archives/%year%/%monthnum%/%day%/%postname%/
In the Optional section you’ll find 2 prefixes used in URLs for category and tag archives:
Category base box enter the custom prefix for your category URLs.
Tags base write the custom prefix for your tag URLs
Don’t forget to click the Save Changes button
After, you should receive two messages regarding your .htaccess
In case your .htaccess is writeable you will receive this message: Permalink structure updated
In case you .htaccess is not writeable you will get this message: You should update your .htaccess